1. Field of the Invention
The present invention relates to public key/private key authentication of images from digital cameras, and more particularly relates to public key/private key authentication of images from digital cameras with global positioning system (GPS) data.
2. Description of the Related Art
Digital cameras have become popular devices for producing high quality digital images of photographic scenes. In general, digital cameras create a digital image by exposure of a CCD sensor array to a photographic scene, followed by conversion of the CCD data to digital image data that is stored in the camera. Thereafter, the digital image data stored in the camera may be transferred to a personal computer or other more permanent storage for printout, viewing, transmission and the like.
One problem with digital image data, however, is the ease with which such data can be manipulated or changed, thereby creating a false representation of the original photographic scene. Such problems are particularly prevalent in certain fields such as forensics and legal or law enforcement fields, where it is essential to prove the authenticity of images. Because of the ease with which digital images may be altered so as to distort the appearance of the original photographic scene, proof of authenticity can often be difficult and sometimes impossible.
Conventional approaches to proving authenticity of digital images have involved the use of public key/private key digital signatures. One such conventional approach is described in U.S. Pat. No. 5,499,294 to Friedman. Friedman's approach involves the use of an embedded private key in a digital camera, with the private key being used to create a digital signature based on a message digest of the image data. Thereafter, a user wishing to authenticate-the image data obtains a public key that corresponds to the embedded private key. As is known in conventional public key/private key authentication, the public key and the private key correspond to each other such that only one public key can decrypt data encrypted with the private key, and vice-versa. Accordingly, through use of the public key, a user of Friedman's system is able to authenticate that image data has not been modified since when it was originally obtained by the digital camera.
One drawback of the Friedman system is its inability also to provide authentication of the photographic event, such as authentication of the time, date and position of the photographic scene involved, at least without visually distorting the digital image of the photographic scene. Specifically, Friedmin's system contemplates an arrangement in which GPS-derived position information is inserted as image data in a frame surrounding the photographic scene. However, such a frame detracts from the visual appearance of the image, making the image less pleasing to the viewer. Moreover, use of such data to authenticate the event is entirely manual, since the data is visual and must be inspected by a human operation. In addition, since the GPS-derived data is actually stored as image data, it is difficult to use the GPS-derived data for other purposes, such as sorting or cataloging.